1. Field
Embodiments of the present invention relate to a display device and a driving method thereof.
2. Description of the Related Art
Recently, various flat panel displays have been developed which are lighter and thinner than cathode ray tubes. Various flat panel displays include a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP), an organic light emitting diode (OLED) display, and the like.
Among the flat panel displays, the OLED display, which displays images by using OLEDs that generate light by recombining electrons and holes, has a fast response speed, is driven with low power consumption, and has excellent emission efficiency, luminance, and viewing angle, such that it has recently been in the spot light.
The OLED includes a thin and transparent indium tin oxide (ITO) anode having a semiconductor characteristic, a metal cathode, and an organic material layer between them. The organic material layer includes a hole transport layer (HTL), an emission layer (EL), and an electron transport layer (ETL). When a voltage with a low voltage characteristic is transmitted from a power source, charges injected into holes of the anode and charges from the cathode are combined on the emission layer to generate electroluminescence on the organic material layer.
Generally, the OLED display is classified as a passive matrix type of OLED (PMOLED) or an active matrix type of OLED (AMOLED), according to how the OLEDs are driven. In aspects of resolution, contrast, and operation speed, the current trend is toward AMOLED displays in which respective unit pixels are selectively turned on or off.
One method for improving peak luminance of the AMOLED, reducing power consumption, and reducing electro-luminescence power capacity is to calculate an image load from input image data and to control the luminance of the entire display panel. The image load is the sum of the image data values for all of the pixels of the display panel. A power source voltage level for the pixel, is controlled to have various levels depending on the image loads in order to guarantee accurate operation of the pixel driving circuit. That is, the level of the power source voltage does not always need to have a relatively-high fixed value, and it is to be prepared for the maximum image load condition in which all the pixels emit as white light (peak light intensity). Average power consumption can be reduced by calculating the image load and determining the power source voltage level.
However, since the luminance of the display panel is totally controlled, the image quality of the display image may be deteriorated according to the displayed pattern for the image data.
The above information disclosed in this Background section is only for enhancement of understanding, and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.